E24: Radiant Heating and Cooling System – Above Green

Requirement Summary

This measure can be claimed if at least 50% of the building area is served by a radiant cooling or heating system.

Intention

Reducing fan energy associated with traditional forced air cooling/ heating systems can reduce operational costs. Occupant comfort can also be improved due to reduction in wide temperature diversities, strong ventilation drafts and fan noise.

Approach/Methodologies

In EDGE, the maximum heat removal capacity of a Radiant System is taken as 50W/m2 of ceiling area. If the cooling or heating load of the building is more than 50W/m2 , the excess load is considered as a secondary system load.

When a user selects the radiant cooling measure, the COP of the cooling system is assumed to increase by 15%. But if a DX or VRV system has been selected in the project, selecting the radiant cooling system will not show any savings. If an Absorption Chiller is selected, it is given first priority and then the radiant system.

No air flow is assumed with a radiant system, therefore, the AHU power for the radiant system is zero.

Potential Technologies/Strategies

Radiation is an effective way of heating or cooling occupants, as it involves heat transfer via infra-red waves absorbed and emitted from various surfaces. The amount of heat transfer is directly proportional to the temperature difference between the surfaces. Human thermal comfort can be achieved by designing some of the surfaces surrounding the occupants to be a bit colder (or warmer, in a heating situation) than the desired temperature. This is done typically by piping cold or hot water to “radiant panels” in the walls, ceiling or floor or in chilled beams. Radiant systems can also be standalone units. For heating, electrically operated or gas-fired panels can also be used.

Radiant systems are especially effective in spaces with large ceiling height and in non-partitioned spaces, where a traditional system will require significant forced air to condition. They are also useful in semi-open spaces, such as outdoor entrances, stadiums, etc. The radiant panels should be installed in such a way that they have a view over the occupants.

Since the radiant systems typically operate at relatively milder temperatures (less than 82ºC for heating and higher than 7ºC for cooling), the cooling/ heating plants can be much smaller. These systems do not depend on air movement for heat transfer, and the ventilation rates can be typically cut down by up to 75% just to meet the fresh air requirements. A Dedicated Outdoor Air System (DOAS), sometimes with energy recovery, can be used to provide this air.

One of the challenges to a radiant cooling system, especially in humid climates, is moisture control. If the surface temperature of the radiant panel drops below the ambient air dew point temperature, water may start condensing on the surface. This could lead to mold growth and other indoor air quality issues. The panel temperature and relative humidity of the indoor space must be properly balanced to avoid this situation.

Radiant systems also require smaller mechanical system spaces and duct sizes. Acoustic quality of the spaces is also improved due to reduction in fan noise.

Relationship to Other Measures

Effectiveness of the Radiant systems can be reduced if the building envelope (including glass) is not sufficiently insulated. In buildings with a large exterior glass area, much of the heat transfer from the radiant panels may be with exterior surfaces, instead of with the desired interior surfaces and occupants. Assumptions The base case for the cooling and heating system comprises of traditional forced air systems, whose efficiency can be found under the Key Assumptions on the Design tab. The efficiency is based on ASHRAE 90.1-2007. The COP of the improved case with a radiant cooling and heating system varies according to the peak cooling load of the project building.

Compliance Guidance

To demonstrate compliance, the design team must provide documentation to support the claims.

Design Stage

Post-Construction Stage

At the design stage, the following must be used to demonstrate compliance:

Manufacturer’s data sheets for the radiant cooling/ heating technology used; and
Mechanical and electrical layout drawings showing the location of the panels, and the output efficiency for system.

At the post-construction stage, the following must be used to demonstrate compliance:

As-built mechanical and electrical drawings with the location of the radiant panels, and the output efficiency of the cooling/ heating system; and
Photographs of installed equipment related to the system; or
Delivery notes showing that specified radiant technology have been delivered to the site.